The invention pertains to methods and apparatus for performing measurements of surface contact potential (workfunction) changes of conductive samples during surface modification of (deposition of different materials or chemical reactions on) such samples.
For a variety of commercially and scientifically significant purposes it is desirable to perform workfunction measurements of a sample. For example, a workfunction value is very sensitive to deposition of different materials on the surface of the sample.
Surface potentials (or workfunctions) can be determined using Kelvin Probe methods. Kelvin Probe methods can provide higher accuracy than other existing methods, but the Kelvin Probe methods requires a vibrating electrode to be placed in close proximity to the surface of the sample. Therefore, Kelvin Probe methods cannot easily be used simultaneously with other sample characterization or modification techniques.
Other methods for workfunction measurements include electron beam current and photoemission methods. Those methods do not require any obstructive electrodes placed in close proximity to the surface of the sample. However, the surface of the sample is subjected to bombardment by electrons or energetic photons. In some cases primary electrons, secondary electrons or UV light may cause unwanted modification of the surface.
We have developed an entirely new method for workfunction measurements, which requires neither electrodes in close proximity to the sample surface, nor sample impinging electrons or UV photons.